Abstract
In this article, we introduce coaxial cables to tune the resonant frequency of metamaterials, the high impedance surfaces (HISs). The proposed structure is used as tuned artificial reflector for radio frequency (RF) coils in magnetic resonance imaging (MRI) machines. In this technique, coaxial cables are connected to the pins (vias) of the HIS to extend their lengths. Circulating the current in long paths aims to increase the total inductance of the HIS to shift its resonance down in frequency. The proposed method for MRI solves the problems of using the available tuning techniques, such as the inaccurate mechanical adjustments which lead to inaccurate electromagnetic properties. Further, it solves the problem of using electronic tuning circuits such as diodes because of the bulk power used by RF coils in MRI which may expose them to damage. In this article, the transverse magnetic reflection coefficient phase at oblique incidence and the transmission coefficient (S2, 1) of the proposed tuned HIS have been investigated. The experimental results showed an obvious shift in the resonant frequency of the tuned HIS compared to the untuned surface.